Mold release film

Abstract

A mold release film according to the present invention includes a base material film and a mold release layer. The mold release layer includes a melamine resin. The melamine resin includes at least one of an imino-type methylated melamine resin, a methylol-type methylated melamine resin, a full ether–type methylated melamine resin, and an imino / methylol-type methylated melamine resin. The mold release layer also includes, relative to the melamine resin, 0–1.5 wt% of a mold release component that is different from the melamine resin. The mold release layer does not substantially include a silicone component. The glass transition temperature of a resin that constitutes the base material film is at least 100°C.

Description

Release film

[0001] The present invention relates to a release film for molding a resin sheet, and more particularly to a release film for molding a resin sheet used for electronic components.

[0002] Conventionally, release films based on polyester film have high heat resistance and mechanical properties and have been used as process films used in solution casting of resin sheets such as adhesive sheets, cover films, polymer electrolyte membranes, and dielectric resin sheets. In recent years, electronic components have become increasingly miniaturized, which has led to a demand for thinner resin sheets used in electronic components. When resin sheets are made thinner, even a small force may be applied when peeling them from the process film. For this reason, release films used as process films have been required to have a small peel force so that they can be peeled without damaging the resin sheet. For this reason, a technology such as that described in Patent Document 1 has been disclosed, proposing a release sheet whose release force on the release layer surface changes little even over a long period of time since the release sheet was manufactured.

[0003] JP 2023-106150 A

[0004] However, in the technology of Patent Document 1, while a small peel force is required so that a resin sheet or the like can be peeled off without damaging it, for example, in electronic component applications, if the peel force is too small, the resin may peel off at an unintended timing, for example, during pre-drying of the resin, which could result in a decrease in yield. To improve these issues, release films with a large peel force have been proposed, but although the resin sheet does not peel off from the release film in the pre-drying step, the resin sheet also does not peel off from the release film after the main drying step, which is a problem in that the original purpose cannot be achieved.

[0005]

[0003] Stability of the release force over time is also required. When the release film is wound into a film roll after coating, pressure is applied in the direction of the core, and some of the release components on the surface of the release layer are transferred to the side opposite the release layer, making it impossible to maintain a constant release force. Therefore, even if a release film with a desired release force is designed, there is a problem that the original purpose cannot be achieved in actual use.

[0006] Furthermore, from the viewpoint of improving productivity, in addition to thinner resin sheets, thinner release films are also required. However, if the release film is thin, when heat or pressure is applied, the release film may deform or wrinkle due to the heat, and the peel force when the resin sheet is peeled from the release film may not be maintained constant, resulting in deformation or tearing of the resin sheet.

[0007] As described above, there is a problem in that existing release films are unable to fully demonstrate their performance, and improvements are required.

[0008] The present invention solves the above-mentioned problems by providing a release film in which the resin sheet does not peel off from the release film during pre-drying, the resin sheet can be peeled off from the release film after main drying without deformation or tearing, and even if the release film is thin, the release film does not deform during the thermal process, and the resin sheet does not deform or tear, and further, the release film has excellent stability of peel force over time.

[0009] As a result of extensive research to solve the above problems, the present inventors have found that the above object can be achieved by a release film having the following configuration, and have completed the present invention.

[0010] That is, the present invention has the following configurations. [1] A release film having a base film and a release layer, wherein the release layer contains a melamine-based resin, and the melamine-based resin contains at least one selected from imino-type methylated melamine resin, methylol-type methylated melamine resin, full-ether-type methylated melamine resin, and imino-methylol-type methylated melamine resin, and the release layer contains a release component different from the melamine-based resin in a ratio of 0 to 1.5 wt % relative to the melamine-based resin, and the release layer is substantially free of silicone components, and the glass transition point of the resin constituting the base film is 100°C or higher. [2] The release film according to [1], wherein the weight-average degree of polymerization of the melamine-based resin is 8.0 or lower. [3] The release film according to [1] or [2], wherein the water contact angle of the release film is 65° or lower. [4] A release film having a peeling speed of 300 mm / min. [5] The release film according to any one of [1] to [3], wherein the tape peel strength at 15000 mN / 50 mm or more and 15000 mN / 50 mm or less is 5000 mN / 50 mm or more. ２ [6] The release film according to any one of [1] to [4] above, wherein the water contact angle (α) of the release layer surface after heating at 180°C for 1 hour and the water contact angle (β) of the release layer surface before heating satisfy the following formula (1): α > β Formula (1). [7] The release film according to any one of [1] to [6] above, wherein the base film is a film obtained by curing a composition containing a polyester resin, and the polyester resin contains naphthalene dicarboxylic acid as a dicarboxylic acid component.

[0011] According to the present invention, a release film is provided in which a resin sheet does not peel from the release film during pre-drying, can be peeled from the release film without deformation or tearing after main drying, and has excellent stability of peel force over time. Furthermore, when heat and pressure are applied to the release film, the release film of the present invention can suppress deformation and wrinkling, even if the release film is thin. Furthermore, for example, the release force can be maintained constant when the resin sheet is peeled from the release film, preventing deformation and tearing of the resin sheet. Therefore, resin sheets produced using the release film of the present invention can be used for electronic components, etc. Furthermore, when a resin composition forming a resin sheet is applied to the release film in a subsequent process and the film is wound up to form a film roll with a resin sheet, the release film of the present invention can suppress the release component transferred to the opposite side of the release layer (e.g., the side of the base film opposite the release layer) from further transferring to the resin surface. Therefore, the problem of the resin sheet's surface properties not being met can be significantly suppressed or avoided.

[0012] As a result of extensive research by the inventors, the present invention provides a release film having a base film and a release layer, wherein the release layer contains a melamine-based resin, and the melamine-based resin contains at least one selected from imino-type methylated melamine resin, methylol-type methylated melamine resin, full-ether-type methylated melamine resin, and imino-methylol-type methylated melamine resin, and the release layer contains a release component different from the melamine-based resin in a ratio of 0 to 1.5 wt % relative to the melamine-based resin, and the release layer is substantially free of silicone components, and the glass transition point of the resin constituting the base film is 100°C or higher.

[0013] (Substrate film) The release film of the present invention comprises a substrate film and a release layer disposed on the surface of the substrate film. When an object to be released is disposed on the release layer of the release film, the object to be released can be formed into the same shape as the substrate film. Furthermore, since the release layer and the object to be released are easily peeled off, the shape of the object to be released can be deformed into and maintained as desired. The release layer may be disposed on one surface or both surfaces of the substrate film.

[0014] In particular, in the present invention, deformation and wrinkling that may occur when heat and pressure are applied to the release film can be suppressed. Furthermore, by achieving these effects, the release film of the present invention can maintain a constant peel force when the resin sheet, which is the release target, is peeled from the release film, thereby suppressing deformation and tearing of the resin sheet. Furthermore, by laminating the base film of the present invention and the release layer in this order, the dimensional stability and surface smoothness of the base film when heated and the thermal shrinkage and expansion properties that the release layer may have when heated can be maintained in a well-balanced manner. Although interpretation should not be limited to a specific theory, if the difference in thermal shrinkage and expansion properties between the release layer and the base film is large, deformation, wrinkling, etc. tend to occur when the release film is heated. In contrast, the combination of the base film and release layer of the present invention can maintain a well-balanced thermal shrinkage and expansion properties of the base film and the release layer, for example, even after heating at 180°C for 1 hour. As a result, the present invention can be suitably used even when the release object is formed through a plurality of drying steps, or even when, for example, one of the drying steps includes a step of storing the resin sheet for a long period of time under high-temperature conditions exceeding 100° C. Furthermore, a release film can be obtained in which the resin sheet does not peel off from the release film during pre-drying, and the resin sheet can be peeled off from the release film after main drying without deformation or tearing, and even if the release film is thin, the release film does not deform in the heat treatment step, and the resin sheet does not deform or tear.

[0015] Known substrates can be used as the substrate film. For example, resin films formed from polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, polyimides, etc. can be used as the substrate. Polyester films are particularly preferred from the standpoint of cost and productivity, with polyethylene terephthalate and polyethylene naphthalate films being more preferred. In one embodiment, the substrate film is a film cured from a composition containing a polyester resin, and the polyester resin contains naphthalene dicarboxylic acid as a dicarboxylic acid component. While not limited to a particular theory, the substrate film containing naphthalene dicarboxylic acid as a dicarboxylic acid component can exhibit excellent dimensional stability, particularly high surface smoothness, even after heating at 180°C for 1 hour, and the release layer according to the present invention can also maintain surface smoothness. A release layer with high surface smoothness after heating allows the resin sheet to be peeled off with a constant peel force, for example, when peeling a resin sheet from the release layer after heating at 180°C for 1 hour. Since the substrate film can maintain high surface smoothness after heating, the heat treatment temperature can be appropriately selected depending on the resin sheet to be manufactured. In one embodiment, in a composition containing a polyester resin, the polyester resin contains naphthalenedicarboxylic acid as a dicarboxylic acid component as a main component.

[0016] The thickness of the base film is preferably 10 μm or more and 188 μm or less, and more preferably 16 μm or more and 100 μm or less. A base film thickness of 10 μm or more can suppress deformation due to heat during production, processing, and molding of the base film. On the other hand, a base film thickness of 188 μm or less can suppress the amount of base film discarded after use while satisfying the physical properties required of the base film, thereby reducing the burden on the environment. Furthermore, a base film thickness of 100 μm or less is preferable because it allows a longer roll of product to be produced in a single production run, improving productivity in terms of base film loss and transportability.

[0017] An easy-adhesion coating may be disposed between the base film and the release layer to improve adhesion, and a coating may be disposed on the surface of the base film opposite to the surface on which the release layer is disposed to impart easy slippage, heat resistance, antistatic properties, etc.

[0018] The average surface roughness (Sa) of the region on which the release layer of the substrate film used in the present invention is laminated is preferably in the range of 1 to 50 nm, more preferably 2 to 30 nm. The maximum protrusion height (P) of the surface on which the release layer of the substrate film used in the present invention is laminated is preferably 2 μm or less, more preferably 1.5 μm or less. When Sa is 50 nm or less and P is 2 μm or less, it is possible to suppress unevenness in the thickness of the release layer and maintain constant smoothness of the release layer surface. Furthermore, it is possible to reduce unevenness in the thickness of the release target object, and to suppress the possibility of tearing starting from a thin portion when the release target object is peeled from the release film.

[0019] The average surface roughness (Sa) of the region opposite the surface on which the release layer of the substrate film used in the present invention is preferably in the range of 3 to 100 nm, more preferably 5 to 30 nm. The maximum protrusion height (P) of the region opposite the surface on which the release layer of the substrate film used in the present invention is preferably 2 μm or less, more preferably 1.5 μm or less. If Sa is 3 nm or more, the slipperiness between the release surface and the non-release surface is improved, resulting in excellent winding properties. Furthermore, if P is 2 μm or less, the release layer surface is not damaged during winding, reducing the possibility of partial peeling of the release layer. Furthermore, the possibility of tearing originating from the peeled portion of the release layer can be suppressed when the release target is peeled from the release film.

[0020] The haze of the substrate film used in the present invention is preferably 0.1% or more and 20% or less, for example, 3% or more and 17% or less, and may be 6% or more and 15% or less. At present, the mechanism has not been analyzed, but it is presumed that by having the above haze value, when the release film is dried at high temperatures, the substrate film can maintain a moderate surface unevenness, which also contributes to the cooling properties of the release film, and the release film tends to exhibit desirable heat resistance. In addition, there is a tendency for the interaction with the release layer of the present invention to be more pronounced.

[0021] The base film of the present invention can be made from recycled raw materials such as polyester film scraps and PET bottles. Because the present invention can use recycled raw materials from such film scraps and PET bottles, the environmental impact can be significantly reduced. Furthermore, even in embodiments that include recycled raw materials from film scraps and PET bottles, the improved slipperiness of the film and ease of air escape can be maintained. The release layer of the present invention can be made by appropriately recovering, processing, and reusing polyester films used in various applications. When such recycled raw materials (materials) are included, the base film may contain fine particles of a size such that the surface average roughness (Sa) of the region on which the release layer is to be laminated is in the range of 1 to 50 nm, and may also contain fine particles of a size such that the surface on which the release layer is to be laminated has a maximum protrusion height (P) of 2 μm or less.

[0022] For example, the size of the fine particles in the base film of the present invention may be in the range of 0.001 μm to 10 μm. Fine particles having a size in this range can satisfy the average surface roughness (Sa) and maximum protrusion height (P) of the region on which the release layer of the base film is laminated. In one embodiment, the base film may have a surface layer that is substantially free of inorganic particles, and the release layer may be laminated on this surface layer.

[0023] The glass transition point of the resin constituting the substrate film used in the present invention is 100°C or higher, more preferably 110°C or higher, and most preferably 115°C or higher. When the glass transition point is 100°C or higher, even when heat or pressure is applied when molding a resin sheet on the release film, the release film itself does not deform and the flatness is maintained, so a resin sheet of uniform thickness can be formed, which is preferable. When the glass transition point is 115°C or higher, it is particularly preferable because a resin sheet of even uniform thickness can be formed without impairing the flatness of the film. The glass transition point is, for example, 150°C or lower, or may be 140°C or lower, or 130°C or lower. In one embodiment, the glass transition point of the resin constituting the substrate film is 110°C or higher and 150°C or lower, for example, 115°C or higher and 140°C or lower, or 115°C or higher and 135°C or lower. By having such properties, the present invention allows the resin sheet to be peeled off with a constant peel force when peeling off the resin sheet or the like from the release layer, even when subjected to a heat treatment at 180°C for 1 hour. In addition, in the case of a film having a glass transition point of less than 100° C., for example, a PET film having a glass transition point of less than 100° C., the surface smoothness of the substrate film tends to be impaired after heat treatment at 180° C. for 1 hour. In addition, there is a risk that the resin sheet will peel off from the release film during pre-drying, and that the resin sheet will deform or break due to deformation of the substrate film after main drying.

[0024] Another specific market demand is the reduction in the cost of release film processing. One way to reduce the cost of release layer processing is, for example, to increase the film conveying speed to achieve high-speed processing. However, in the present invention, increasing the conveying speed can lead to deterioration in the winding shape, such as winding slippage, and therefore requires increasing the tension during conveyance, which could make the film more susceptible to wrinkling during conveyance. Furthermore, since the film's residence time in the oven is shortened, the amount of heat applied to the film decreases, resulting in issues such as insufficient drying leading to insufficient curing of the release layer and blocking of the film roll due to insufficient curing. In the present invention, the glass transition point of the resin constituting the substrate film is 100°C or higher, making it possible to increase the temperature of the drying oven. For example, the present invention can avoid the problem of the film being more susceptible to wrinkling during conveyance due to increased drying heat, which could occur with conventional combinations of substrate film and release layer. Furthermore, since the glass transition point of the resin constituting the substrate film is 100°C or higher, the substrate film is less likely to wrinkle even when the coating tension or drying temperature is increased, allowing the release film to be processed at high speed, contributing to cost reduction.

[0025] The water vapor permeability of the substrate film used in the present invention is 1.0 g / m ２ ・d or more 25.0g / m ２ d, and 3.0 g / m ２ ・d or more 15.0g / m ２ d, more preferably 5.0 g / m ２ ・d or more 10.0g / m ２ By setting the water vapor transmission rate within the above range, when a release layer is formed on a substrate film, a release film having a desired peel strength without unevenness or stickiness can be formed. ２ By having a water vapor permeability of d or more, as will be described later, when a coating solution containing a solvent is applied to form a release layer on the substrate film, the drying of the solvent proceeds efficiently, and unevenness and stickiness on the surface of the release film due to insufficient drying are suppressed, which is preferable. On the other hand, although the detailed mechanism is not clear, ２It is believed that by keeping the drying time at or below d, the solvent does not volatilize suddenly during drying, but rather volatilizes over a certain period of time, which allows the release component in the coating liquid to be efficiently oriented on the surface of the release layer, thereby forming a release film having the desired release force. The water vapor permeability in the present invention can be evaluated, for example, by the water vapor permeability measured when the substrate film is 25 μm thick.

[0026] The Martens hardness (HMT115) of the substrate film used in the present invention is 150 N / mm ２ More than 400N / mm ２ Preferably, it is 170 N / mm or less. ２ More than 370N / mm ２ More preferably, it is 200 N / mm or less. ２ 350N / mm or more ２ By setting the Martens hardness of the substrate film within the above range, when a release film is produced by providing a release layer on the substrate film and used as a process paper for a resin sheet or the like, it is possible to provide a release film that can prevent deformation of the object to be released when the object to be released is peeled off. ２ By satisfying the above, the elastic modulus of the release film becomes large, and when the object to be released is peeled off from the release film, the release film does not deform following the object to be released, so that excessive stress is not applied to a part of the object to be released, and the object can be peeled off with a uniform force, and deformation of the object to be released can be prevented. On the other hand, when the Martens hardness (HMT115) of the base film is 400 N / mm ２ It is preferable that the thickness is not more than 100 μm, since this results in good handleability and ease of handling.

[0027] (Release Layer) The release layer of the present invention contains a melamine-based resin, as described below. Furthermore, the release layer of the present invention contains a release component different from the melamine-based resin in a ratio of 0 to 1.5 wt % relative to the melamine-based resin. That is, the release layer of the present invention does not contain a release component different from the melamine-based resin, or contains a release component different from the melamine-based resin in a ratio of 1.5 wt % or less relative to the melamine-based resin. Furthermore, the release layer does not substantially contain a silicone component. In one embodiment, the release layer contains a release component different from the melamine-based resin in a ratio of 0.05 wt % to 1.5 wt % relative to the melamine-based resin. For example, the release component is contained in a ratio of 0.1 wt % to 1.5 wt %. By satisfying these conditions, for example, in release films for producing electronic components such as ceramic capacitors, release films for molding resin sheets containing epoxy resins, release films for forming all-solid-state batteries, and release films for molding resin sheets having a urethane structure, it is possible to provide a good balance between the peeling force with respect to the object to be peeled and the adhesion (holding force) with respect to the object to be peeled.

[0028] (Release Component of Release Layer) The release component used to form the release layer of the present invention includes, for example, an acrylic resin. Furthermore, the acrylic resin contained in the release layer of the present invention preferably has a long-chain alkyl group. The release properties can be controlled by orienting the long-chain alkyl group contained in the acrylic resin on the surface of the release layer. In particular, the acrylic resin of the present invention can exhibit good wettability with, for example, a resin composition forming a resin sheet. Furthermore, the acrylic resin of the present invention can provide a release film that does not peel off from a release target, such as a resin sheet formed on a release layer, during the pre-drying process and has easy releasability after the main drying process. The acrylic resin of the present invention may further include a methacrylic resin, for example, a polymer of methyl methacrylate (methyl methacrylate = MMA) or a copolymer with an acrylic ester (acrylate). Furthermore, for example, the molecular weight of the acrylic resin preferably exceeds 500.

[0029] By adjusting the release component content of the release layer to 0 to 1.5 wt%, the water contact angle of the release film surface is reduced and wettability is improved, making it easier to coat even with resins that tend to cause cissing during coating, which is preferable. Furthermore, by adjusting the release component content to 0 to 1.5 wt%, the release strength of the release film is appropriately increased, making it possible to provide a release film that does not peel off from a release target, such as a resin sheet formed on the release layer, during the pre-drying process but has easy releasability after the main drying process. For example, the above-mentioned effects can also be achieved in an embodiment in which the release layer contains a release component different from the melamine-based resin in a ratio of 0.05 wt% to 1.5 wt% relative to the melamine-based resin.

[0030] In the present invention, the pre-drying step refers to the state after heating at a temperature of 100°C for 2 minutes, and the main drying step refers to the state after heating at a temperature of 180°C for 15 minutes. In addition, in the present invention, "after heating" does not only mean immediately after heating, but also means a state after cooling to an ambient temperature or lower (for example, 40°C or lower). Furthermore, the main drying may be performed in multiple stages.

[0031] Furthermore, the release layer according to the present invention is substantially free of silicone components. This prevents the silicone components from transferring to the object to be released, thereby preventing, for example, contamination of the object by silicone and preventing malfunction of electronic devices due to the object to be released. For example, by being substantially free of silicone compounds, migration of silicone to the product can be avoided when the release film of the present invention is wound into a roll, thereby reducing adverse effects on the final product. As used herein, "substantially free of silicone components" means that silicone components are not intentionally added to the components forming the release layer. For example, there is a possibility that a trace amount of silicone components, etc., may be present unintentionally during the manufacturing process of the release layer. For example, in the present invention, "substantially free of silicone compounds" is defined as a content of 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit, when the Si element is quantified by fluorescent X-ray analysis. "This is because even if silicone components are not actively added to the release layer, contaminants from foreign matter or dirt adhering to the raw resin or the production line or equipment during the film manufacturing process may peel off and become mixed into the release layer. The detection limit varies depending on the measuring device, but when the Si element is quantified by fluorescent X-ray analysis, the Si element may be 0.01 ppm or more. For example, it may be 0.01 ppm or more and 50 ppm or less. Furthermore, if a very small amount of silicone is contained in the release layer, the coefficient of friction when the front and back surfaces of the film are rubbed together is reduced, improving the air resistance when the film roll is wound, improving the wound shape of the film roll, and preventing damage to the quality and appearance of the film roll.

[0032] (Resin Components of Release Layer) The resin component A used to form the release layer of the present invention contains a melamine-based resin. Furthermore, it may contain resin components other than the melamine-based resin component as long as the characteristics of the present invention are not impaired. Examples of resin components other than the melamine-based resin component include polyisocyanate resins, epoxy resins, aluminum chelates, titanium chelates, and ultraviolet-curable resins. It contains at least 50% by mass of a melamine-based resin, and other resins can be appropriately blended.

[0033] The release layer preferably contains a melamine-based resin, because the cured film is rigid and has excellent chemical resistance, weather resistance, and heat resistance. Crosslinking with aluminum chelate or titanium chelate may be undesirable depending on the application, due to the inclusion of metal components. Furthermore, in the present invention, by using a melamine-based resin as the resin for the release layer, the resin sheet can be held without peeling from the release film during pre-drying, and after drying, the resin sheet can be peeled from the release film without deformation or breakage. Although the detailed mechanism has not been analyzed, it is believed that the melamine-based resin undergoes a certain degree of self-reaction due to the drying heat during coating. It is then speculated that, under heating conditions, for example, at 180°C for 1 hour, the self-reaction is further accelerated, causing the release layer to shrink during curing, changing the surface morphology and increasing the water contact angle. As a result, it is speculated that the resin sheet can be held without peeling from the release film during pre-drying, and after drying, the resin sheet can be peeled from the release film without deformation or breakage.

[0034] The melamine-based resin used in the release layer of the present invention can be a common one, and is not particularly limited. However, it is preferably obtained by condensing melamine with formaldehyde and having one or more triazine rings and one or more methylol groups and / or alkoxymethyl groups per molecule. Specifically, a compound obtained by subjecting a methylol melamine derivative obtained by condensing melamine with formaldehyde to a dehydration condensation reaction with a lower alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or butyl alcohol to etherification is preferred. Examples of methylol melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine. One or more types may be used.

[0035] In order to increase the reactivity of the melamine resin and obtain a more rigid cured film, it is preferable to use a methylol-type methylated melamine or a hexaalkoxymethyl melamine, which have more reactive sites per molecule. However, a hexaalkoxymethyl melamine, which has superior reactivity, is more preferable, and it is particularly preferable to use hexamethoxymethyl melamine. In this case, hexamethylol melamine is a melamine represented by the following formula (a), in which X is a methylol group (-CH ２ Hexaalkoxymethylmelamine is a compound obtained by dehydration condensation of a methylolmelamine derivative with an alcohol, and X is (-CH ２ -OR, R is an alkyl group having 1 to 4 carbon atoms). Hexamethoxymethylmelamine is a compound in which X is (-CH ２ -OMe).

[0036]

[0037] In the above (a), each X may be the same or different. Also, each R may be the same or different. Also, X may be (—H).

[0038] The melamine resin used in the present invention is preferably not a single compound but a mixture of multiple compounds. Based on the structure of the compound that is the main component of the melamine compound, it is possible to select an imino type (X=-H), a methylol type (X=-CH ２ -OH), full ether type (X = -CH ２ Melamine-based resins can be broadly classified into imino-methylol types (wherein R is an alkyl group having 1 to 4 carbon atoms) and imino-methylol types. The melamine-based resin includes at least one selected from imino-methylated melamine resins, methylol-methylated melamine resins, full-ether-methylated melamine resins, and imino-methylol-methylated melamine resins. In one embodiment, from the viewpoint of reactivity, full-ether types and methylol types are preferred, with full-ether types being more preferred. Among full-ether types, hexamethoxymethylmelamine (CAS No. 3089-11-0), in which R is a methyl group, is most preferred. The use of a melamine-based compound with a higher content of this hexamethoxymethylmelamine results in higher reactivity, a higher crosslink density, and a more rigid cured film.

[0039] Furthermore, the present invention can provide a release film that exhibits excellent stability of release force over time. By including a release component in a ratio of 0 to 1.5 wt % relative to the melamine-based resin, the release film of the present invention can minimize the amount of release component transferred to a release target, such as a resin sheet, or to manufacturing equipment. Therefore, when a resin composition for forming a resin sheet is applied to the release film and then wound up to form a film roll with a resin sheet, such as in a post-process, the release component transferred to the opposite side of the release layer (e.g., the side of the substrate film opposite the release layer) can be prevented from further transferring to the surface of the resin sheet. Therefore, the problem of the resin sheet's surface properties not being met can be significantly reduced or avoided. For example, although such effects should not be interpreted as being limited to a particular theory, it is speculated that the dicarboxylic acid component contained in the base film contributes to a higher Tg of the base film compared to a PET film, so that the flatness of the film is not impaired even when the film is processed at high temperatures. When the film is rolled, stress concentration in the winding direction due to the impairment of the flatness of the film can be avoided, and the transfer of release components to the resin sheet can be suppressed even when stored for a long period of time. Furthermore, by using a melamine-based resin in the release layer, a rigid cured film with a high crosslinking density can be formed, which prevents unreacted release components in the release layer from bleeding out to the surface even when stored for a long period of time, thereby suppressing the transfer of release components to the resin sheet. It is also speculated that the interaction between the melamine-based resin contained in the release layer and the base film also contributes to the production of the above-mentioned effects.

[0040] The melamine resin used in the present invention preferably has a weight-average degree of polymerization of 8.0 or less, more preferably 6.0 or less, even more preferably 3.0 or less, and most preferably 2.0. Although the detailed mechanism has not been analyzed, a weight-average degree of polymerization of 8.0 or less is preferable because the self-reaction of the melamine resin proceeds sufficiently, resulting in a rigid cured film. Furthermore, in the present invention, a weight-average degree of polymerization of 2.0 or less is preferable because an even more rigid cured film is obtained. If the weight-average degree of polymerization is 8.0 or more, a cured film with sufficient strength cannot be obtained. When a release layer is formed using this melamine resin to produce a release film, when a solvent-containing resin composition is applied to form a resin sheet on the release film, a portion of the release layer may dissolve in the solvent of the resin composition, potentially preventing the release film from exhibiting its inherent performance. For example, the weight-average degree of polymerization may be 1.1 or more, or even greater than 1.5.

[0041] Melamine resins contain imino groups (-NH ２ Even if these melamine derivatives are mixed, as long as the weight-average polymerization degree of the melamine resin is within the above range, the reactivity is excellent and each can be suitably used.

[0042] The melamine used in the present invention may be commercially available, for example, Cymel 300, Cymel 301, Cymel 303LF, Cymel 350, Cymel 370N, Cymel 771, Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 701, Cymel 266, Cymel 267, Cymel 285, Cymel 232, Cymel 235, Cymel 236, Cymel 238, Cymel 272, Cymel 212, Cymel 253, Cymel 254, Cymel 202, Cymel 207 (manufactured by Allnex Japan Co., Ltd.), Nikalac MW-30M, Nikalac MW-30, Nikalac MW-30HM, Nikalac MW-390, Examples of such resins include Nikalac MW-100LM, Nikalac MA-1-750LM, Nikalac MW-22, Nikalac MS-21, Nikalac MS-11, Nikalac MW-24A-1, Nikalac MS-001, Nikalac MA-1-002, Nikalac MA-1-730, Nikalac MA-1-750, Nikalac MA-1-708, Nikalac MA-1-706, Nikalac MA-1-042, Nikalac MA-1-035, Nikalac MA-1-45, Nikalac MA-1-43, Nikalac MA-1-417, and Nikalac MA-1-410 (manufactured by Nippon Carbide Corporation). Among these, full-ether type methylated melamine resins are preferred in terms of low-temperature, short-time curing properties and adhesion to polyester films. Commercially available products include Cymel 303LF and Nikalac MW-30.

[0043] In the present invention, it is preferable to add an acid catalyst to the release layer in order to promote the crosslinking reaction of the melamine-based compound, and it is preferable to add the acid catalyst to the composition for forming the release layer, apply it, and then cure it. The acid catalyst to be used is not particularly limited, and any existing acid catalyst can be used, but it is preferable to use a sulfonic acid-based catalyst.

[0044] As the sulfonic acid catalyst, for example, p-toluenesulfonic acid, xylenesulfonic acid, cumenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, trifluoromethanesulfonic acid, etc. can be suitably used, and p-toluenesulfonic acid is particularly suitable from the viewpoint of reactivity.

[0045] Sulfonic acid catalysts have higher acidity and better reactivity than other acid catalysts such as carboxylic acid catalysts, and therefore can process the release layer at lower temperatures, which is preferable because it can prevent the film from losing flatness and the rolled appearance from being deteriorated due to heat during processing.

[0046] In the present invention, the mass of the acid catalyst contained in the release layer is 0.1 to 20.0 wt% relative to the melamine-based resin. In one embodiment, the mass of the acid catalyst is 0.1 wt% or more and 20.0 wt% or less relative to the melamine-based resin, for example, 0.5 wt% or more and 10.0 wt% or less, or even 1.0 wt% or more and 5.0 wt% or less. By controlling the mass of the acid catalyst within the above range, the peel strength of the release film can be controlled within the desired range. When the mass of the acid catalyst is 0.1 wt% or more relative to the melamine-based resin, the self-reaction of the melamine-based compound is promoted, the hardening of the release film progresses, and stickiness and film roll blocking are suppressed, which is preferable. Furthermore, when the mass of the acid catalyst is 20.0 wt% or less relative to the melamine-based resin, the release film after hardening has appropriate adhesion, and when a resin sheet is provided on the release film, unintended peeling of the resin sheet at times such as pre-drying or transport processes is prevented, which is preferable. If the mass of the acid catalyst is 20.0 wt% or more relative to the melamine-based resin, the catalyst may volatilize and contaminate the drying equipment when the resin solution for forming the release layer is applied to the substrate film and then placed in the drying equipment for drying, which is not preferred. It is more preferred that the mass of the acid catalyst is 10.0 wt% or less, even more preferably 7.0 wt%, and most preferably 3.3 wt% or less.

[0047] The sulfonic acid catalyst used in the present invention may be commercially available. Examples of commercially available products include Dryer (registered trademark) 900 (p-toluenesulfonic acid, manufactured by Hitachi Chemical Co., Ltd.), NACURE (registered trademark) DNNDSA series (dinonylnaphthalene disulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), NACURE (registered trademark) DNNDSA series (dinonylnaphthalene (mono)sulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), NACURE (registered trademark) DDBSA series (dodecylbenzenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.), and NACURE (registered trademark) p-TSA series (p-toluenesulfonic acid, manufactured by Kusumoto Chemicals Co., Ltd.).

[0048] The release layer of the present invention may contain additives such as an adhesion improver and an antistatic agent, as long as the effects of the present invention are not impaired. In order to improve adhesion to the substrate film, it is also preferable to subject the surface of the polyester film to pretreatment such as anchor coating, corona treatment, plasma treatment, or atmospheric pressure plasma treatment before providing the release layer.

[0049] The thickness of the release layer is preferably 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 1 μm or less. If the thickness of the release layer is less than 0.01 μm, it is difficult to form the release layer uniformly, and the peeling force may become unstable. On the other hand, if the thickness of the release layer exceeds 10 μm, the proportion of recycled raw materials used decreases, which is uneconomical and undesirable.

[0050] The average surface roughness (Sa) of the region of the release layer is preferably in the range of 1 to 50 nm, more preferably 2 to 30 nm. The maximum protrusion height (P) of the surface of the base film used in the present invention on which the release layer is laminated is preferably 2 μm or less, more preferably 1.5 μm or less. When Sa is 50 nm or less and P is 2 μm or less, unevenness in the thickness of the release layer can be suppressed and the smoothness of the surface of the release layer can be maintained constant, thereby suppressing the possibility of tearing starting from the thin portion when the release object is peeled from the release film. Furthermore, the rate of change of the average surface roughness (Sa) of the region and the maximum protrusion height (P) before and after heating is preferably within 20%, more preferably within 10%, and even more preferably within 5%. If the rate of change in the area surface average roughness (Sa) or the maximum protrusion height (P) before and after heating is within 20%, the adhesion area between the release layer and the object to be released increases after heating, and the anchor effect reduces the possibility of heavy peeling when peeling the object to be released from the release layer, which is preferable.

[0051] In the present invention, the method for forming the release layer is not particularly limited, and a method is used in which a coating liquid in which a release resin is dissolved or dispersed is spread on one side of a polyester film of a base film by coating or the like, and the solvent is removed by drying, followed by heat drying, heat curing, or ultraviolet curing. In this case, the drying temperature during solvent drying and heat curing is preferably 180°C or less, more preferably 160°C or less, and most preferably 140°C or less. The heating time is preferably 30 seconds or less, more preferably 20 seconds or less, and even more preferably 10 seconds or less. When it is 180°C or less, the flatness of the film is maintained and there is little risk of uneven thickness of the release layer, which is preferable. When it is 140°C or less, the film can be processed without impairing the flatness of the film, and there is a further reduction in the risk of uneven thickness of the release layer, which is particularly preferable.

[0052] In the present invention, the coating liquid for forming the release layer is not particularly limited, but it is preferable to add a solvent having a boiling point of 70° C. or higher. Adding a solvent having a boiling point of 70° C. or higher can prevent bumping during drying, level the coating film, and improve the flatness of the coating film surface after drying. The amount of solvent added is preferably about 50 to 99% by mass based on the total amount of the coating liquid.

[0053] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0054] The release film obtained in the present invention preferably has a tape peeling force in the range shown below.

[0055] The release film obtained by the present invention may have a tape peel strength of 5,000 mN / 50 mm or more and 15,000 mN / 50 mm or less at a peeling speed of 300 mm / min, for example, 7,500 mN / 50 mm or more and 14,000 mN / 50 mm or less, or 10,000 mN / 50 mm or more and 13,000 mN / 50 mm or less. While not limited to a specific theory, in the present invention, a tape peel strength within the above range can be achieved by adjusting the mass of the acid catalyst contained in the release layer to within a range of 0.1 to 20.0 wt% relative to the melamine-based resin. A tape peel strength within the above range is preferable, for example, because when a resin sheet is formed, it can be peeled without deformation or tearing. A tape peel strength of 5,000 mN / 50 mm or more is preferable because it reduces the possibility of peeling at unintended times, such as during a pre-drying process of the resin sheet. Furthermore, a tape peeling force of 15,000 mN / 50 mm or less is preferable because the release object is less likely to deform when peeled off. The tape peeling force refers to the tape peeling force at a peeling speed of 300 mm / min., and can be used to evaluate the peeling force when peeling off an object to be released, such as a pressure-sensitive adhesive (e.g., acrylic pressure-sensitive adhesive tape (Nitto Denko Corporation, No. 31B)) placed on the release layer according to the present invention. The tape peeling force can be measured at room temperature (25°C).

[0056] The release film obtained in the present invention preferably has a water contact angle in the range shown below.

[0057] The release film obtained by the present invention preferably has a water contact angle of 65° or less on the surface of the release layer, for example, 40° or more and 70° or less, or 50° or more and 65° or less. Within the above range, for example, when a resin sheet is formed, it can be peeled off without deformation or tearing, which is preferable. A water contact angle of 65° or less is preferred because it is less likely to peel off at an unintended time, such as in a pre-drying process of the resin sheet. Furthermore, a water contact angle of 40° or more is preferred because it is less likely to deform the release target object when it is peeled off. The above water contact angle is a numerical range measured at room temperature, and corresponds to the water contact angle (β) of the release layer surface before heating, which will be described later.

[0058] In the release film obtained in the present invention, the water contact angle (α) of the release layer surface after heating at 180° C. for 1 hour and the water contact angle (β) of the release layer surface before heating preferably satisfy the following formula (1): α>β Formula (1)

[0059] In the present invention, the water contact angle (α) of the release layer surface after heating refers to the water contact angle measured after heating the release film at 180°C for 1 hour. In the present invention, by performing the drying temperature when forming the release layer on the substrate film under the conditions described in this specification, the formula (1) regarding the water contact angle can be satisfied. Furthermore, the release layer of the present invention can be used as a release film in a state in which the release layer is formed on the substrate film. However, the present inventors have discovered that, as a feature of the present invention, for example, when the release film of the present invention is used as process paper, the curing of the release film can be promoted and the surface morphology of the release layer can be controlled during the heat treatment process when forming a resin sheet. The present inventors have found that the releasability of the release layer can be changed after the production of the release film and during the resin sheet formation process, and have found the relationship of formula (1) regarding the water contact angle as an indicator of this. Furthermore, by satisfying the relationship of the above formula (1), at room temperature, a resin sheet-forming composition or a film-like resin sheet precursor can be adhered to the release layer on the release film, and the adhesion of the resin sheet during production can be maintained with heating, ultimately suppressing deformation of the release object, allowing the release object to be released satisfactorily. In this way, curing in the release film further progresses during heat treatment, causing cure shrinkage of the release layer and changing the surface morphology, thereby increasing the water contact angle. As a result, a slight gap is formed between the release film and the resin sheet, reducing the possibility of deformation of the release object when it is peeled off. Furthermore, rather than simply increasing the water contact angle by heating, it is necessary to satisfy formula (1) regarding the water contact angle, and the present invention can achieve such a relationship. The heat treatment temperature for the resin sheet may be, for example, 180°C for 1 hour.

[0060] In one embodiment, the difference |(α)-(β)| between the water contact angle (α) of the release layer surface after heating at 180°C for 1 hour and the water contact angle (β) of the release film before heating is 1.1 or more, for example, 1.7 or more. The upper limit may be, for example, 7.0 or less, or 4.0 or less. Although the detailed mechanism has not been explored, by satisfying these conditions, curing in the release film further progresses during heat treatment, causing cure shrinkage of the release layer and changing the surface morphology, thereby increasing the water contact angle. As a result, a slight gap is formed between the release film and the resin sheet, reducing the possibility of deformation of the release object when it is peeled off. Furthermore, it is presumed that the surface morphology does not change significantly on a nanoscale. Therefore, the effects of the present invention can be particularly demonstrated in release films for manufacturing electronic components such as ceramic capacitors, release films for molding resin sheets containing epoxy resins, release films for forming all-solid-state batteries, and release films for molding resin sheets having a urethane structure. Furthermore, the release object can be peeled off without damaging it.

[0061] The release film obtained in the present invention has a release layer with a Martens hardness (HMT115) of 200 N / mm ２ More than 1500N / mm ２ Preferably, it is 300 N / mm or less. ２ More than 1250N / mm ２ More preferably, it is 350 N / mm or less. ２ More than 1000N / mm ２ By setting the Martens hardness (HMT115) of the release layer within the above range, when the release film is used as a process paper such as a resin sheet, it is possible to provide a release film that can prevent deformation of the object to be released when the object is peeled off. ２ As a result of the above, when the object to be released is peeled off from the release film, the release layer does not deform to follow the object to be released, so excessive stress is not applied to any part of the object to be released, and the object can be peeled off with a uniform force, preventing deformation of the object to be released.

[0062] In the release film obtained by the present invention, by combining the base film and the release layer so that the Martens hardness of each falls within the above-mentioned range, the resin sheet does not peel off from the release film during pre-drying, and the resin sheet can be peeled off from the release film without deformation or breakage after main drying. Furthermore, because of this relationship, even if the release film is thin, it is possible to obtain a release film in which the release film does not deform during the heat treatment step, and the resin sheet does not deform or break.

[0063] It is preferable that the release film obtained in the present invention is such that the resin sheet does not peel off from the release film when the resin sheet peel force is measured under the pre-drying process conditions. If the resin sheet does not peel off from the release film, for example, when the resin sheet is formed, there is a low possibility that the resin sheet will peel off at an unintended timing such as the pre-drying process, which is preferable.

[0064] When the release film obtained by the present invention is subjected to a resin sheet peel force measurement under the post-drying process conditions, the peel force is preferably 1000 mN / 50 mm or less, more preferably 500 mN / 50 mm or less, and most preferably 300 mN / 50 mm or less. It may also be 5 mN / 50 mm or more, or 10 mN / 50 mm or more. Within the above range, the release object is less likely to deform when it is peeled off after heating in the post-drying process or the like, which is preferable.

[0065] In the present invention, the pre-drying process refers to the state after heating at a temperature of 100°C for 2 minutes, and the post-drying process refers to the state after heating at a temperature of 180°C for 15 minutes. In addition, in the present invention, "after heating" does not only refer to immediately after heating, but also to a state after cooling to ambient temperature or below (e.g., 40°C or below). The resin sheet peeling force refers to the resin sheet peeling force at a peeling rate of 300 mm / min., and can be used to evaluate the peeling force when peeling off a release target object placed on the release layer of the present invention, such as a resin sheet (e.g., a resin sheet formed by curing an epoxy resin, etc.). Furthermore, the tape peeling force can be measured at room temperature (25°C).

[0066] In the present invention, a laminated film (a release film with a resin sheet) can be obtained by providing a resin sheet on at least one side of a release film. The laminated film can be obtained, for example, by applying a resin composition to at least one surface of the release film of the present invention, drying it as necessary, and forming a resin sheet on at least one side of a substrate film. For example, a resin sheet can be provided on the surface of the release layer opposite the substrate film.

[0067] The present invention can also be applied to other uses, such as battery components, pressure-sensitive adhesive layer protection (protection for OCA (Optical Clear Adhesive), protection for pressure-sensitive adhesive tape, separators for transdermal drug patches in the medical field, casting paper used in the manufacturing process of semiconductor-related parts such as circuit boards, casting paper used in the manufacturing process of electronic parts such as ceramic capacitors, and protection of image display members, and similar effects are expected.

[0068] In one embodiment, the release film of the present invention, due to the properties of the components contained in the release layer, can better exhibit the effects of the present invention in a release film for producing electronic components such as ceramic capacitors, a release film for molding resin sheets containing epoxy resins, a release film for forming all-solid-state batteries, and a release film for molding resin sheets having a urethane structure.

[0069] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. The property values ​​used in the present invention were evaluated using the following methods.

[0070] <Evaluation> (Tape Peeling Strength) An adhesive tape ("31B" manufactured by Nitto Denko Corporation) was attached to the surface of a release film, and after pressing with a pressure roller at a linear pressure of 5 kgf / mm, the tape was left for 20 hours under conditions of a temperature of 22°C and a humidity of 60%. The release film to which the adhesive tape was attached was cut into a strip of 25 mm wide and 150 mm long. One end of the adhesive tape was fixed, one end of the release film was supported, and the release film side was pulled at a speed of 300 mm / min to measure the T-peel strength. A tensile tester ("AUTOGRAPHAG-A-1" manufactured by Shimadzu Corporation) was used for the measurement.

[0071] (Water Contact Angle) The contact angle of water in contact with the surface of the release layer was measured under conditions of 22° C. and 60% RH using a contact angle meter ("Fully Automatic Contact Angle Meter DM-701" manufactured by Kyowa Interface Science Co., Ltd.).

[0072] (Water contact angle after heating) Using a contact angle meter ("Fully automatic contact angle meter DM-701" manufactured by Kyowa Interface Science Co., Ltd.), the release film was placed in an oven set at 180°C, and after 1 hour, it was removed from the oven and left to cool to room temperature. The contact angle of water in contact with the surface of the release layer was measured under conditions of 22°C and 60% RH.

[0073] (Martens Hardness of Substrate Film) The substrate film was cut to a size of 0.5 mm x 0.5 mm, fixed to a glass plate using adhesive tape, and subjected to a load-unload test using a dynamic ultra-microhardness tester (DUH-211S, manufactured by Shimadzu Corporation). From this measurement, the Martens hardness (HMT115) was calculated using the following formula (average value of n = 10): HMT115 = F / (26.43 × h ２ ) (N / mm ２ ) (F: load (N), h: indentation depth (mm)) (Measurement conditions) Indenter used: diamond regular triangular pyramidal indenter (edge ​​angle: 115°) Measurement mode: load-unload test Test force: 500 mN Minimum test force: 1.96 mN Load rate: 7.0 mN / sec Load holding time: 5 sec Unload holding time: 5 sec Measurement atmosphere: 25±1°C, 65±5% RH Measurement number: 10

[0074] (Martens Hardness of Release Layer) The resin and crosslinker mixed composition to be used as a sample was prepared using a mixed solvent (25°C) of 50% by mass of toluene and 50% by mass of MEK so that the solid content concentration was 20% by mass. The coating liquid was applied to the surface of a glass slide using a wire bar to prepare a glass slide sample with a coating layer thickness of 3.0 μm. The glass slide sample was left to stand for 5 minutes in a hot air circulating oven set to a temperature of 130°C and then removed for heat treatment. A load-unload test was performed on the surface of the obtained sample using a dynamic ultra-microhardness tester (DUH-211S, manufactured by Shimadzu Corporation). From this measurement, the Martens hardness (HMT115) was calculated using the following formula (average value of n = 10): HMT115 = F / (26.43 × h ２ ) (N / mm ２ ) (F: load (N), h: indentation depth (mm)) (Measurement conditions) Indenter used: diamond regular triangular pyramidal indenter (edge ​​angle: 115°) Measurement mode: indentation depth setting load-unload test Minimum test force: 0.002 mN Load speed: 0.0150 mN / sec Load holding time: 3 sec Unload holding time: 3 sec Indentation depth: 0.1 μm Measurement atmosphere: 25±1°C, 65±5% RH Measurement number: 10

[0075] (Resin sheet peel force under pre-drying process conditions: PF1) An epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828) was used as the resin, and a phenolic resin (manufactured by DIC Corporation, phenol novolac, TD-2090-60M, 60% solids MEK solution) was used as the crosslinking agent in a ratio of 1:2, and MEK was further added to adjust the solids concentration to 60.0% by mass, thereby obtaining a resin coating liquid. The obtained resin coating liquid was applied to the surface of a release film using an applicator, and then dried at 100°C for 2 minutes to form a release film with a resin sheet having a thickness of 50.0 μm. An adhesive tape (manufactured by Nitto Denko Corporation, "31B") was bonded to the resin surface of the obtained resin-bonded release film, and the resin sheet-bonded release film with the adhesive tape bonded thereto was cut into strips having a width of 25 mm and a length of 150 mm. One end of the adhesive tape was fixed, one end of the release film with the resin sheet was supported, and the release film with the resin sheet was pulled at a speed of 300 mm / min to measure the T-peel strength. For the measurement, a tensile tester ("AUTOGRAPHAG-A-1" manufactured by Shimadzu Corporation) was used.

[0076] (Resin sheet peeling force under post-drying process conditions: PF2) Measurement was carried out in the same manner as (Resin peeling force in pre-drying process), except that the drying conditions were changed to heating at a temperature of 180° C. for 15 minutes.

[0077] (Film Flatness) A film sample 1 m wide x 10 m long cut from the center of the width direction of the release film was placed under a three-wavelength fluorescent lamp so that the width direction of the film sample was parallel to the axial direction of the elongated three-wavelength fluorescent lamp, and the reflection of the three-wavelength fluorescent lamp on the film sample was visually inspected. The image of the three-wavelength fluorescent lamp reflected on the film sample was evaluated as O if there were heat wrinkles after heating the film sample at 180°C for 15 minutes, or if the image of the three-wavelength fluorescent lamp was distorted or intermittent. If the image of the three-wavelength fluorescent lamp was almost linear, it was evaluated as O. If the image was slightly distorted and / or intermittent, it was evaluated as Δ.

[0078] (Glass Transition Point) The glass transition point (extrapolated onset temperature) of a polymer was measured using a DSC (EXSTAR6000 manufactured by Seiko Instruments Inc.) with a sample amount of 10 mg at a temperature rise rate of 20° C. / min.

[0079] A release layer coating solution was obtained by adding a melamine resin (Nippon Carbide Corporation, full-ether type methylated melamine resin, Nikalac MW-30) as the resin component (A) and paratoluenesulfonic acid (Hitachi Chemical Polymer Co., Ltd., Dryer #900) as the curing catalyst in the amounts shown in Table 1, and then adding a solvent (toluene / MEK = 50 / 50: mass ratio) to adjust the solids concentration to 12.0 mass%, thereby obtaining a release layer coating solution. A polyethylene naphthalate film (Toyobo Co., Ltd., Q5100, thickness: 25 μm, surface roughness (Sa): 0.006 μm, haze: 12.6%) was used as the substrate film.

[0080] (Formation of Release Layer) The obtained release layer coating liquid was applied to a substrate film using a gravure coater, and then dried at 130°C for 30 seconds to form a release layer with a thickness of 0.3 µm. The obtained release film was subjected to the above-mentioned evaluations. Various compositions and evaluation results are shown in Tables 1 and 2.

[0081] (Weight-average polymerization degree of melamine-based resin) Analysis conditions: 16 mg of a sample was weighed and dissolved in 8 ml of chloroform. The solution was filtered through a 0.2 μm membrane filter, and the resulting sample solution was subjected to GPC analysis under the following conditions: Apparatus: TOSOH HLC-8320GPC Column: K-G+ K-802 (exclusion limit molecular weight 5×10 ３ ) + K-801 (exclusion limit molecular weight 1.5 x 10 ３ ) (Shodex), Solvent: chloroform 100% Flow rate: 1.0 ml / min Concentration: 0.2% Injection volume: 50 μL Temperature: 40° C. Detector: RI

[0082] The weight average molecular weight was calculated in terms of polystyrene, and the weight average degree of polymerization was calculated based on that value. PStQuick C (TOSOH) from the PStQuick series was used as the polystyrene. Among the polystyrenes added to PStQuick C (TOSOH), polystyrenes Mw 2110000, 427000, and 37900, which greatly exceed the column's exclusion limit molecular weight, were excluded from the preparation of the calibration curve.

[0083] Examples 2 to 4 A release layer was formed in the same manner as in Example 1, except that the composition was changed to that shown in Table 1. The obtained release films were subjected to the above-mentioned evaluations.

[0084] Example 5 A release layer was formed in the same manner as in Example 3, except that the resin component (A) was changed to a melamine resin (Nikalac MS-11, a methylol-type methylated melamine resin, manufactured by Nippon Carbide Corporation). The obtained release film was subjected to the above-described evaluations.

[0085] Example 6 A release layer was formed in the same manner as in Example 5, except that the resin component (A) was changed to a melamine resin (Nippon Carbide Corporation, imino-methylated melamine resin, Nikalac MW-24X). The obtained release film was subjected to the above-described evaluations.

[0086] Example 7 A release layer was formed in the same manner as in Example 6, except that the resin component (A) was changed to a melamine resin (Nippon Carbide Corporation, imino-methylol type methylated melamine resin, Nikalac MS-001). The obtained release film was subjected to the above-described evaluations.

[0087] Example 8 A release layer was formed in the same manner as in Example 7, except that the resin component (A) was changed to a melamine resin (Nippon Carbide Corporation, imino-methylol type methylated melamine resin, Nikalac MX-750). The obtained release film was subjected to the above-described evaluations.

[0088] (Comparative Example 1) (Preparation of acrylic resin (B) and release layer coating liquid) Stearyl acrylate (CH ２ =C(H)COOC １８ H ３７), hydroxyethyl acrylate (CH ２ =C(H)COOC ２ H ４ OH) were mixed in a ratio of 90:10, toluene was added so that the solids concentration was 40% by mass, and 0.5 mol% of azobisisobutyronitrile (AIBN) was added under a nitrogen stream to copolymerize, obtaining an acrylic resin (B). In the formulations shown in Table 1, a melamine resin (manufactured by Nippon Carbide Corporation, full-ether type methylated melamine resin, Nikalac MW-30) was added as the resin component (A), acrylic resin B was added as the release component, and paratoluenesulfonic acid (manufactured by Hitachi Chemical Polymer Co., Ltd., Dryer #900) was added as the curing catalyst, and a solvent (toluene / MEK = 50 / 50: mass ratio) was added to obtain a release layer coating liquid with a solids concentration of 12.0% by mass. A release layer was formed in the same manner as in Example 1, except that the release layer coating liquid was changed as described above, and the resulting release film was subjected to the above-mentioned evaluations.

[0089] Comparative Example 2: A release layer coating solution was obtained by adding a blocked isocyanate (manufactured by Baxenden) as the resin component (A), MD1200 (manufactured by Toyobo Co., Ltd.) as the other component (binder component), and a solvent (water / IPA = 5 / 3: mass ratio) to the resin component (A), resulting in a solids concentration of 4.0 mass%. A polyethylene naphthalate film (manufactured by Toyobo Co., Ltd., Q5100, thickness: 25 μm, surface roughness (Sa): 0.006 μm, haze: 12.6%) was used as the substrate film. The obtained release layer coating solution was applied to the substrate film using a gravure coater, and then dried at 150 °C for 30 seconds to form a release layer with a thickness of 0.3 μm. The obtained release film was subjected to the above-mentioned evaluations.

[0090] Reference Example 1 A polyethylene terephthalate film (manufactured by Toyobo Co., Ltd., E5100, thickness: 38 μm, surface roughness (Sa): 0.0365 μm (corona-treated surface), maximum surface cross-sectional height (St): 3.72, haze: 3.7%) was used as the base film, and a release layer was formed in the same manner as in Example 3, except that the release layer coating liquid was applied to the corona-treated surface. The obtained release film was subjected to the above-mentioned evaluations.

[0091] (Reference Examples 2 and 3) A release layer was formed in the same manner as in Example 1, except that the composition was changed to that shown in Table 1. The obtained release films were subjected to the above-mentioned evaluations.

[0092]

[0093]

[0094] <Evaluation Results> The present invention provides a release film in which the resin sheet does not peel off from the release film during pre-drying and can be peeled off from the release film after drying without deformation or breakage. Furthermore, when heat or pressure is applied to the release film, the release film of the present invention can suppress deformation and wrinkles, even when the release film is thin. On the other hand, in Comparative Example 1, the content of the release component other than the melamine-based resin was outside the range of the present invention, so the tape peeling force was significantly reduced and the resin sheet peeled off under pre-drying conditions. In Comparative Example 2, the resin component did not contain melamine resin but instead contained isocyanate, so tape could not be peeled off after application. Similarly, the resin sheet could not be peeled off. In Reference Example 1, the base film used was PET without naphthalenedicarboxylic acid, and it was confirmed that the flatness of the film was slightly impaired compared to the present invention. In Reference Example 2, the amount of catalyst was too small, so the release layer was not sufficiently cured and did not exhibit its intended performance. In Reference Example 3, preliminary verification had shown that the material exhibited properties equivalent to those of Example 4. However, the large amount of catalyst used could have caused contamination of the drying equipment, so verification was discontinued midway.

[0095] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.

[0096] To provide a release film in which a resin sheet does not peel off from the release film during pre-drying, and the resin sheet can be peeled off from the release film after drying without deformation or breakage, and even if the release film is thin, the release film does not deform in a heat step, and the resin sheet does not deform or break.

Claims

1. A release film having a base film and a release layer, wherein the release layer contains a melamine resin, and the melamine resin contains at least one selected from imino-type methylated melamine resin, methylol-type methylated melamine resin, full-ether-type methylated melamine resin, and imino-methylol-type methylated melamine resin, and the release layer contains a release component different from the melamine resin in a ratio of 0 to 1.5 wt % relative to the melamine resin, and the release layer is substantially free of silicone components, and the glass transition point of the resin constituting the base film is 100°C or higher.

2. The release film according to claim 1, wherein the weight average degree of polymerization of said melamine resin is 8.0 or less.

3. The release film according to claim 1, wherein the water contact angle of said release film is 65° or less.

4. The release film according to claim 1, wherein the tape peel strength at a peeling speed of 300 mm / min is 5,000 mN / 50 mm or more and 15,000 mN / 50 mm or less.

5. The Martens hardness of the base film used in the release film is 150 N / mm ２ The release film according to claim 1 or 2, wherein 6. The release film according to claim 1, wherein the water contact angle (α) of the release layer surface after heating at 180°C for 1 hour and the water contact angle (β) of the release layer surface before heating satisfy the following formula (1): α>β 7. The release film according to claim 1, wherein the base film is a film obtained by curing a composition containing a polyester resin, and the polyester resin contains naphthalenedicarboxylic acid as a dicarboxylic acid component.

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